The manufacture of objects which are best suited for packaging in a stacked arrangement is commonplace in the United States, as well as other countries throughout the world. Machines have been created that can manufacture such objects at great cycle rates. Often it is desirable to stack these objects in identical, predetermined count-size stacks—for example, stacks of 25 plates or 30 cups or 20 lids, etc. This is particularly useful when the objects are to packaged for direct wholesale or retail sale.
However, there have been significant restraints on the ability to accurately and quickly count stacked objects. This may stem, in part, from the apparent lag of the technology employed to accurately count stacked objects behind the machines used to manufacture and stack the objects. Often, as a default, the stacked objects are counted manually. Obviously, this has a number of drawbacks including labor and speed.
There have been some forays into the development of apparatus that would automatically count and stack objects. However, these prior art devices are either non-optimal—by creating numerous restraints on the process of forming, counting, stacking, and packaging of nestable objects—or are overly complex—requiring additional moving parts, space, or both.
One non-optimized restraint of the prior art has been the speed at which stacking systems operate. Often, they are required to operate at a slower rate than the potential for the manufacturing machines, necessitating the slow down of the entire process. Slowed production rates can have a significant negative impact on a company's profitability.
Another restraint concerns the accuracy of the object count in stacks. Prior art stackers have been unable to consistently and readily stack a predetermined number of objects. As a result, either a double check is required, costing more time and energy, or the products are shipped off with an incorrect number of objects in any particular stack, to the possible detriment of a company's reputation.
Still another restraint of concern is reliability. Ideally, the stacker should work every time to create a stack with the correct number of objects. However, complexity of mechanics may result in frequent down-time and increased maintenance costs. Further, the complex machines require human labor to either supervise the machine's operation or participate in the stacking process. This may create difficulties including increased labor costs, slower operation, and the possibility of injury.
The prior art has failed to provide adequate solutions to alleviate all of these restraints. One attempt at forming stacks with a predetermined count is disclosed in U.S. Pat. No. 4,545,714, issued to Johnson et al. This patent describes a pneumatically-operated feed conduit which has containers blown therethrough by using a pneumatic blowing device, and propelled to a first location to form a nested stack of containers. While at a first location, the containers are sensed by a photoelectric device. The nested containers are then conveyed to a second station located vertically below the first wherein a plurality of rotating resilient elements contact the edge of each of the containers to advance them downward. A conveyor drive, adapted to coact with the resilient elements at a higher linear speed, engages an end of one of the containers with a projecting member to separate the stack. A predetermined count is achieved by having the projecting member interact at a specific time interval with the rotating resilient elements.
U.S. Pat. No. 4,802,808, issued to Wolk et al., describes a stacking apparatus for deep-drawn articles of plastics. The '808 patent discloses a lower stacking plate and an upper stacking plate which are adapted to receive formed articles from a forming die. The lower and upper stacking plates are used to form a vertical stack of formed articles. The upper stacking plate, including a stack of formed articles, can be raised to a position on the working level of a removal station. The removal station has a support plate that moves forward underneath the raised stack, a pushing device that is above the support plate that moves parallel relative to the support plate, and a tilting frame located adjacent the support plate when the support plate is in the forwardly moved position. The tilting frame tilts about a horizontal axis from an upright receiving position to a laterally directed discharge position.
U.S. Pat. No. 5,234,313, issued to DelDuca, discloses a method for automatically counting and stacking trimmed molded articles. The '313 patent describes a trim press and an apparatus for stacking articles trimmed by the trim press. The apparatus for stacking includes a frame, a carriage mounted to the frame, at least one stacking mechanism, and a moving mechanism for transporting the completed stack of articles from within the die shoe of the stationary die member to a position for removal from the apparatus.
U.S. Pat. No. 6,241,457, issued to Huttig et al., discloses a stacking apparatus for a thermoforming machine. The '457 patent describes a lower stacking plate that picks up articles ejected from a thermoforming machine. The Huttig device has an upper stacking plate juxtaposed with the lower stacking plate, and complementary thereto, for receiving deep-drawn articles from the lower stacking plate and for retaining a column of the articles. A pivot arm carries the upper stacking plate; the upper stacking plate is raisable and lowerable on the pivot arm. A carriage having guide rollers has the pivot arm articulated to it for swingable movement about an arm pivot. A support has a guide bar swingably mounted at a horizontal pivot axis. The guide bar is engaged by the rollers for guiding the carriage therealong, whereby a column of the articles on the upper stacking plate is swingable from a receiving position to a deposition position. The patent also discloses means for securing the guide bar selectively in a first angular position about the horizontal pivot axis in which the upper stacking plate is constrained to deposit columns of the covers forming the articles in a vertical orientation on the surface and columns of the cups forming the articles in a horizontal orientation on the surface.
Each of the above-cited references has failed to provide a simplistic answer to the problem of reliably, accurately and efficiently counting stacked objects. The apparatus and methods of the present invention overcome the disadvantages of these and other prior art devices and techniques. The present invention is focused on performing at a speed substantially equal to modern thermoforming machines. It is fully automated, accurate and precise in its formation of stacked objects of a predetermined number. It is also reliable and easily maintained and adjustable. Furthermore, it requires a relatively small amount of physical space, opening up that space for other uses.